THE ADRENAL GLANDS 81 



ables of biology. Then some observations were made which 

 threw doubt upon a long accepted fact, now declared a dogma. 

 Lately, opinion has veered back to immortality. But in the case 

 of a close relative of the ameba, the one-celled animal known as 

 the Paramecium, union with another Paramecium, true conjuga- 

 tion, has been proved necessary to prevent death sooner or later. 

 Sex here appears in its most primitive form, on the basis of ex- 

 change of necessary materials, between individuals to prevent 

 death, their own having been, so to speak, worn out, in the course 

 of metabolism. 



Specifically different sexes come later, when mortality is a uni- 

 versal fate, as a means of rebirth and escape from death. Then 

 the sexes develop their latest function, most prominent among 

 the younger vertebrates, of acting as nature's most potent method 

 of variation and differentiation. In the pursuit of the different, 

 nature has exalted sex, and the intensity of the sex life. As far 

 as the preservation of a species is concerned, and the reproduc- 

 tion of the individual, the asexual methods, budding, for example, 

 would have done well enough. But when it comes to enacting 

 a different individual apart from the effects of environment, sex 

 stands out as the favored method of Life. 



The development of the sexes and the sexual life brought a new 

 element of conflict into the living world. Before the advent of 

 the sexes the conflict was essentially for the means of existence, 

 food alone. But with the sexual life came a conflict for sex 

 pleasure, a competition among members of the same species for 

 the same individual as their sex partners. The result was the 

 introduction of a factor in evolution which Darwin examined so 

 closely in the "Descent of Man." 



The sex conflict has been the cause for the origin and the 

 survival of certain physical and mental traits, helpful in sex 

 attraction, sex combat, the growth of the embryo, and the nutri- 

 tion and safety of the young of a species, — in short, the whole 

 process of sexual selection. The proportions of the skeleton, the 

 distribution of hair and fat, the construction of organs of attack 

 and defense, the color of the skin, the cyclic processes of prepara- 

 tion for impregnation, the oestrus or heat period in animals, the 

 menstrual period in the human being, the psychic reactions to 

 danger and combat have all been thus determined. That man is 

 bearded while woman is not, — that woman has potentially func- 

 tional breasts while man has not, — the aggressive pugnacity of 

 man contrasted with the more passive timidity of woman, have 



